L-2013-325, SL2-20 Steam Generator Tube Inspection Report RAI Reply

SL2-20 Steam Generator Tube Inspection Report RAI Reply

ML13338A582
Person / Time
Site:	Saint Lucie
Issue date:	11/26/2013
From:	Katzman E Florida Power & Light Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-2013-325
Download: ML13338A582 (5)

Text

November 26, 2013 L-2013-325 10 CFR 50.55a FPL. 10 CFR 50.36 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 Re: St. Lucie Unit 2 Docket No. 50-389 SL2-20 Steam Generator Tube Inspection Report RAI Reply

Reference:

1. FPL Letter L-2013-130 dated May 6, 2013, "Refueling Outage SL2-20 Steam Generator Tube Inspection Report"(NRC ADAMS Accession # ML13141A479)

2. NRC Email Letter from Siva Lingam to Ken Frehafer "St. Lucie Unit 2 - Requests for Information (RAI) on Steam Generator Tube Inspection Report for Outage No. SL2-20 (TAC No. MF1786). (NRC ADAMS Accession # ML13310B664) - Dated November 6, 2013 Florida Power & Light (FPL) submitted the St. Lucie Unit 2 Technical Specification 6.9.1.12 steam generator tube inspection report for the winter 2012 refueling outage (SL2-20) via letter L-2013-130 dated May 6, 2013 (Reference 1). Via Reference 2 above, the NRC staff forwarded a request for additional information (RAO). This letter provides FPL's response to the RAI.

Please contact Ken Frehafer at (772) 467-7748 should you have any questions regarding this submittal.

Sincerely, Eric S. Katzman Licensing Manager St. Lucie Plant.

Attachment ESK/KWF Aod Florida Power & Light Company 6501 S. Ocean Drive, Jensen Beach, FL 34957

L-2013-325 Attachment Page 1 of 4 NRC RAI #1:

Please discuss the results of the following inspections/operations that were performed in RFO20 (in 2012).

a. Upper Bundle Flush

b. Sludge Lance

c. Foreign object search and retrieval (FOSAR)

d. Operation and Maintenance warranty inspections, including the upper internals FPL Response:

a. Upper Bundle Flush (UBF) was performed on both Steam Generators (SGs).

b. Sludge Lancing was performed on both SGs.

As a result of UBF and sludge lancing, a total of 123 lbs of sludge were removed from the SGs (77.5 lbs from SG A, and 45.5 lbs from SG B). Based on the pre and post sludge lancing visual inspections, the UBF and sludge lancing processes appeared to be very effective in removing deposits from the upper bundle and tube sheet regions.

c. FOSAR was performed on both SGs, after sludge lancing was completed.

No foreign objects were detected during SG A FOSAR.

One metallic object (.75" in length) was retrieved from the hot leg top of tubesheet annulus in SG B.

No known foreign objects remain in either SG.

In addition to the FOSAR visual examinations, the periphery tubes around the annulus and along the tube-free divider lane were examined with the +PointTM probe at the top-of-tubesheet locations, in both SGs. No degradation due to foreign objects was reported during these inspections.

d. As part of the operation and maintenance inspections, the following locations were visually inspected in both SGs:

1) Recirculation Pipe Flange Assembly

2) Feedring Inspection Port Covers (replaced during RFO19 in 2011)

3) Wrapper Room Hatches

4) Manway Hatch to top of Dryers

5) Dryer Vanes and Primary Cyclones

L-2013-325 Attachment Page 2 of 4

6) Loose Parts Trapping System.

No degradation or concerns were identified for the wrapper room hatches, the upper manway hatch to the top of the'dryers, or the recirculation pipe flange assembly.

The feedring inspection port covers were replaced in both SGs during RFO19 in 2011 as a result of loosening during normal operations. No abnormalities or loose hardware was observed during the RFO20 inspections in 2012.

The primary cyclones and secondary separator dryer vanes were visually inspected and showed no signs of damage, degradation or erosion/corrosion. The secondary separators were free of fouling.

During Steam Drum inspections, two metallic objects (one 2.5" in length, and one 5.5" in length) were retrieved from the Loose Parts Trapping System (LPTS) screens in the SG B Steam Drum. The LPTS screens were in sound and intact condition.

NRC RAI #2:

In your report, you discuss that a tube in SG B was plugged for wear at a V-shaped support pad, because there was no qualified eddy current technique for depth sizing that specific type of flaw. Please discuss how you confirmed that this tube had adequate integrity if no qualified sizing technique exists and the tube was not in-situ pressure tested.

FPL Response:

An extended technique was used to size the V-Shape support pad related indication for integrity assessment purposes. Section 4.4 of EPRI Report 1019038 "Steam Generator Management Program: Steam Generator Integrity Assessment Guidelines Revision 3" discusses the use of extended techniques for tube integrity applications. Section 4.4 states:

"To satisfy CM and OA, it may sometimes be necessary to extend techniques that are qualified for a particular application to other applications where they have not been formally qualified under... (EPRI Report 1013706)". For example, if an existing degradationmechanism has no applicable ETSS, a qualified technique would have to be used. When extending techniques, a justification shall be documented".

L-201 3-325 Attachment Page 3 of 4 An existing technique was evaluated for detection of V-Shape support pad wear and determined to be acceptable for extended application for this wear mechanism. This technique was extended for sizing for Condition Monitoring (CM) purposes, but not for service, based on an engineering evaluation of the wear morphology. This justification is documented in the site technique qualification document.

The extended application technique was used to establish the Condition Monitoring limit for V-Shape support pad wear at the required upper 95-50 sizing value. The NDE depth fell below the Condition Monitoring limit for meeting the structural integrity performance criteria margin requirement of three times the Normal Operating Pressure Differential (3xNOPD). This calculated result was confirmed by comparing the +PointTM probe voltage for the indication against the voltage screening parameters given in Section 4 of the EPRI In Situ Pressure Testing Guidelines. The indication voltage was below the threshold voltage for proof test and leakage screening for volumetric flaws. Therefore, in situ pressure testing was not required based on minimum 95-50 burst pressure calculation and by the voltage screening threshold criteria.

NRC RAI #3:

Please discuss the results of the supplemental U-bend rotating +PointTM probe data and whether it confirmed/supported the root cause of the wear at the anti-vibration bars (AVBs) (i.e., distortion of the AVBs during fabrication).

FPL Response:

During RFO20 in 2012, AVB gap measurements were performed with the +PointTM probe in 86 tubes. The AVB gap analysis neither supported nor refuted the conclusion of the root cause report.

During the supplemental examinations, it was observed that the presence of wear at some of the locations would distort the signal amplitude. In addition, the gap values calculated during the supplemental examinations represent cold-shutdown conditions, not operating conditions.

The AVB gap measurement study performed during RFO20 in 2012 does not change the conclusion of the root cause report.

L-2013-325 Attachment Page 4 of 4 NRC RAI #4:

Please discuss whether the tubes with wear indications at AVB 4 in row 69 were left in service.

FPL Response:

There were 14 tubes total with indications at AVB 4 in Row 69 (12 tubes in SG A, and 2 tubes in SG B). None of the indications at those locations required plugging, and all 14 affected tubes were left in service.

All of the wear indications at AVB 4 reported in row 69 during RFO20 in 2012 were initially reported at RFO19 in 2011. There were no new wear indications at AVB 4 in Row 69 (in either SG) during the RFO20 inspection in 2012. Since the RFO21 inspection (scheduled for 2014) includes 100% bobbin probe examination, all of the locations with AVB 4 / Row 69 locations will be re-inspected and monitored for change.